Modulation of a Two-Level-System Landscape Per Experiment

The subject disclosure relates to two-level-system (TLS) quantum noise, and more specifically to modulation of a TLS landscape per experiment.

Accurate estimation of observables within a quantum circuit is a fundamental aspect for many quantum algorithms. That is, when quantum circuits are executed on quantum processors, the quantum circuits yield observable estimates of properties or quantities of a quantum system. When executed on noisy quantum processors, though, the quantum circuits yield observable estimates that deviate from ideal values. Accordingly, mitigation of the impact of such noise can help obtain unbiased estimates. However, achieving accurate measurements and device stability for various quantum applications can be challenging due to noise fluctuations caused by interactions between superconducting qubits and TLSs.

The above-described background description is merely intended to provide a contextual overview regarding the TLS landscape in quantum computing and is not intended to be exhaustive.

The following presents a summary to provide a basic understanding of one or more embodiments described herein. This summary is not intended to identify key or critical elements, delineate scope of particular embodiments or scope of claims. Its sole purpose is to present concepts in a simplified form as a prelude to the more detailed description that is presented later. In one or more embodiments described herein, systems, computer-implemented methods, apparatus and/or computer program products that enable modulation of the two-level-system (TLS) interaction landscape between successive executions are discussed.

According to an embodiment, a system is provided. The system can comprise a memory that can store computer-executable components. The system can further comprise a processor that executes at least one of the computer executable components that can execute a quantum circuit to obtain measurements of a qubit. The at least one of the computer executable components can further modulate, via a control TLS knob, a TLS landscape of a quantum processor between successive executions of the quantum circuit.

According to various embodiments, the above-described system can be implemented as a computer-implemented method or as a computer program product.

The following detailed description is merely illustrative and is not intended to limit embodiments and/or application or uses of embodiments. Furthermore, there is no intention to be bound by any expressed or implied information presented in the preceding Background or Summary sections, or in the Detailed Description section.

One or more embodiments are now described with reference to the drawings, where like referenced numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a more thorough understanding of the one or more embodiments. It is evident, however, in various cases, that the one or more embodiments can be practiced without these specific details.

According to an embodiment, a system is provided. The system can comprise a memory that can store computer-executable components. The system can further comprise a processor that executes at least one of the computer executable components that can execute a quantum circuit to obtain measurements of a qubit. The at least one of the computer executable components can further modulate, via a control TLS knob, a TLS landscape of a quantum processor between successive executions of the quantum circuit. Such embodiments of the system can provide a number of advantages, including reducing computational overhead, increasing stability of error mitigation, reducing computational time of quantum experiments, reducing quantum noise, and enabling scalability of quantum systems.

In one or more embodiments of the aforementioned system, the at least one of the computer executable components can further supply a periodic modulation that continuously varies of the control TLS knob during the successive executions of the quantum circuit based on a period of the periodic modulation. Such embodiments of the system provide the advantage of reducing computational time of quantum experiments and computational overhead.

In some embodiments of the aforementioned system, the at least one of the computer executable components can further discretely change parameters of the control TLS knob between the successive executions of the quantum circuit. Such embodiments of the system provide the advantage of stabilizing qubit operation and stabilizing qubits against background fluctuations of TLSs.

In various embodiments of the aforementioned system, the at least one of the computer executable components can further select, based on a metric, subsets of the measurements to determine subsets of the parameters of the control TLS knob, and execute the quantum circuit using the subsets of the parameters. Such embodiments of the system provide the advantages of reducing qubit noise, error sources, and stabilizing qubits against background fluctuations of TLSs.

In some embodiments of the aforementioned system, wherein the period is determined by an experimental repetition rate at which the measurements are obtained, gate length, or a shape of modulation on the TLS landscape. Such embodiments of the system provide the advantage of stabilizing qubits against background fluctuations of TLSs.

In one or more embodiments of the aforementioned system, wherein the periodic modulation of the control TLS knob is non-commensurate relative to the experimental repetition rate. Such embodiments of the system provide the advantage of increasing stability of observable estimates in quantum experiments.

In one or more embodiments of the aforementioned system, the at least one of the computer executable components can further modulate the TLS landscape of one or more qubits of the quantum circuit via one or more respective control TLS knobs, wherein parameters of the periodic modulation and the shape of modulation on the TLS landscape is independent between the one or more respective control TLS knobs. Such embodiments of the system provide the advantage of reducing qubit noise fluctuation, enabling scalability to larger sets of quantum circuits for quantum applications. The stabilized noise provided by such embodiments further provides the advantage of obtaining more accurate solutions for a given quantum application via quantum error mitigation.

In one or more embodiments of the aforementioned system, wherein the measurements from each of the successive executions over the TLS landscape at different modulations are accumulated. Such embodiments of the system provide the advantages of reducing qubit noise and stabilizing noise models for execution in quantum experiments.

According to some embodiments, the above-described computer system can be implemented as a computer-implemented method or as a computer program product.

Reliable operation in quantum computing can depend on characterizations of qubits to assess stability or performance. Characterization of qubits can provide insights into various parameters, such as coherence times, gate fidelity, and error rates, which are essential for optimizing algorithms, identifying hardware limitations, and advancing quantum technology (e.g., quantum error mitigation, qubit fabrication). For example, quantum error mitigation (e.g., probabilistic error cancellation) relies on the stability of learned noise models. However, there can be various sources of error (e.g., noise model drift) in observable estimation of the qubits. Such sources of error can cause unstable results, and thus can limit how many quantum circuits can be executed and accordingly how many noise models can be reliably learned. For example, the decoherence time of qubits is subject to time fluctuations due to TLSs and defects that reside in dielectrics that are part of the qubit devices. In particular, the diffusion of TLS transition frequencies over time can significantly contribute to fluctuations in qubit relaxation times. Such temporal fluctuations can cover vast ranges of timescales, causing characterization of the qubits to be difficult, as measuring the decoherence time of a qubit once is insufficient to accurately and meaningfully characterize the qubit device. In TLSs, the qubit-TLS interaction can degrade reliability and effectiveness of error mitigation techniques (e.g., can result in nonphysical observable estimates). As another example, such sources of error can cause inaccurate observable measurements for qubit characterization, limiting abilities to determine or refine qubit fabrication techniques.

The TLS landscape can be changed via a control TLS knob to mitigate such errors. However, modulating the TLS landscape over an entire experiment using only one control TLS knob value can lead to oversimplified control and bias. Such an approach may fail to capture the complex and multifaceted nature of quantum systems, limiting the ability to optimize performance or explore alternative configurations of the quantum devices. Thus, an efficient method for stabilizing qubits against temporal fluctuations in a TLS based on modulation of the TLS landscape between successive executions can be desirable.

Various embodiments of the present disclosure can be implemented to produce a solution to one or more of the problems discussed above. Embodiments described herein include systems, computer-implemented methods, and computer program products that can enable modulation of a qubit-TLS interaction landscape. For example, in various embodiments, a periodic modulation can be supplied to a control TLS knob during execution of a quantum circuit to effectively sample different TLS environments for each repetition in the execution over the duration of data collection. In various embodiments, the periodic modulation can periodically vary during execution based on a period of the periodic modulation. Furthermore, to enable the different TLS environments for each experiment repetition, the periodic modulation can be non-commensurate to an experiment repetition rate of the quantum experiment. As another example, in various embodiments, discrete modulation of can be supplied to the control TLS knob during execution of the quantum circuit to also sample different TLS environments for each repetition. In some embodiments, calibrated parameters of the control TLS knob can be determined based on a metric of observed measurables and used to calibrate the control TLS knob to implement the calibrated parameters for discrete modulation of the TLS landscape. This can allow the control TLS knob to only utilize parameters that will cause stable or desirable results of the metric.

In various embodiments, more than one control TLS knob can be supplied continuous or discrete modulation to enable different TLS environments for each experiment repetition of more than one qubit. In some embodiments, the qubit-TLS interaction landscape of each of the more than one qubit can be independently modulated. In other words, the qubit-TLS interaction landscape can be individually controlled in multi-qubit scenarios.

illustrates a block diagram of an example, non-limiting systemthat can facilitate modulation of a qubit-TLS interaction landscape between successive executions in accordance with one or more embodiments described herein. That is, the non-limiting systemcan facilitate modulation of a qubit-TLS interaction landscape, in combination with employment of a quantum system().

Aspects of systems (e.g., systemand the like), apparatuses or processes in various embodiments of the present invention can constitute one or more machine-executable components embodied within one or more machines (e.g., embodied in one or more computer readable mediums (or media) associated with one or more machines). Such components, when executed by the one or more machines, e.g., computers, computing devices, virtual machines, etc. can cause the machines to perform the operations described. Systemcan comprise noise stabilization component, processor, memory, system bus, execution component, and modulation component.

The systemand/or the components of the systemcan be employed to use hardware and/or software to solve problems that are highly technical in nature (e.g., related to quantum error mitigation, TLS modulation, quantum noise models, qubit fabrication, qubit characterization, etc.), that are not abstract and that cannot be performed as a set of mental acts by a human. Further, some of the processes performed may be performed by specialized computers for carrying out defined tasks related to quantum systems. The systemand/or components of the system can be employed to solve new problems that arise through advancements in technologies mentioned above, computer architecture, and/or the like. The systemcan provide technical improvements to qubit characterization by stabilizing qubit-TLS interactions, improving efficiency of qubit characterization, and/or reducing computational overhead etc.

Discussion turns briefly to processor, memoryand busof system. For example, in one or more embodiments, the systemcan comprise processor(e.g., computer processing unit, microprocessor, classical processor, and/or like processor). In one or more embodiments, a component associated with system, as described herein with or without reference to the one or more figures of the one or more embodiments, can comprise one or more computer and/or machine readable, writable and/or executable components and/or instructions that can be executed by processorto enable performance of one or more processes defined by such component(s) and/or instruction(s).

In one or more embodiments, systemcan comprise a computer-readable memory (e.g., memory) that can be operably connected to the processor. Memorycan store computer-executable instructions that, upon execution by processor, can cause processorand/or one or more other components of system(e.g., noise stabilization component, execution component, and/or modulation component) to perform one or more actions. In one or more embodiments, memorycan store computer-executable components (e.g., noise stabilization component, execution component, and/or modulation component).

Systemand/or a component thereof as described herein, can be communicatively, electrically, operatively, optically and/or otherwise coupled to one another via bus. Buscan comprise one or more of a memory bus, memory controller, peripheral bus, external bus, local bus, and/or another type of bus that can employ one or more bus architectures. One or more of these examples of buscan be employed. In one or more embodiments, systemcan be coupled (e.g., communicatively, electrically, operatively, optically and/or like function) to one or more external systems (e.g., a non-illustrated electrical output production system, one or more output targets, an output target controller and/or the like), sources and/or devices (e.g., classical computing devices, communication devices and/or like devices), such as via a network. In one or more embodiments, one or more of the components of systemcan reside in the cloud, and/or can reside locally in a local computing environment (e.g., at a specified location(s)).

In addition to the processorand/or memorydescribed above, systemcan comprise one or more computer and/or machine readable, writable and/or executable components and/or instructions that, when executed by processor, can enable performance of one or more operations defined by such component(s) and/or instruction(s).

In various embodiments, systemcan access a quantum circuit, and execution componentcan execute the quantum circuiton a quantum processor (e.g. processor). In various aspects, quantum circuitcan comprise any suitable number of qubits, wherein the qubits can be superconducting qubits. Superconducting qubits are a basic and fundamental element of superconducting quantum computers or superconducting quantum systems. In various cases, the qubits can be physically instantiated in any suitable way. For example, the qubits can be realized as an anharmonic electrical resonator (e.g., a resonant circuit that deviates from ideal harmonic behavior and exhibits non-linear relationships between frequency and energy levels). In various embodiments, the qubits can be implemented using TLSs (e.g., quantum system with two distinguishable energy levels that can represent computations basis states of a qubit). Transitions between the two basis states can often be induced by external factors such as electromagnetic radiation, temperature changes, modification of the strain in material, or interactions within the quantum system.

In various aspects, it can be desirable to characterize one or more qubits of the quantum circuit. In various embodiments, execution componentcan repeat execution of quantum circuitany suitable number of times (e.g.,repetitions) to obtain measurements of a qubit of the quantum circuitto characterize the qubit. In other words, execution componentcan perform any suitable number of successive executions of the quantum circuit. As a non-limiting example, it can be desirable to measure the energy relaxation time (e.g., decoherence time) of a qubit, denoted by T. The energy relaxation time of a qubit is a basic coherence characterization of a qubit, representing a timescale over which the qubit's quantum state remains coherent before losing phase relationship due to interactions with its environment. As another example, Randomized Benchmarking (RB) can be used to characterize performance of single-qubit or two-qubit gates in quantum circuitby performing a series of randomized gate sequences to measure fidelity of the resulting states. In any case, the execution componentcan execute quantum circuitto obtain observable measures to characterize the qubits. In various embodiments, a measurement can be obtained for each repetition of execution (e.g., shot) of the quantum circuit.

In various embodiments, the modulation componentcan stabilize the measurements obtained by successively executing the quantum circuitover a number of repetitions. More specifically, modulation componentcan supply a periodic modulation that continuously varies to a control TLS knob. In some instances, the periodic modulation can be a quasi-static periodic modulation (e.g., gradual and continuous adjustment of parameters with minimal change over time). The control TLS knob represents parameters that can manipulate the qubit-TLS interaction landscape of the quantum processor. The control TLS knob can be implemented in any suitable format.

As a non-limiting example, the control TLS knob can be implemented via piezo electronics to provide lattice deformation. Specifically, shape and dimensions of lattice structures surrounding the TLS can be precisely controlled with piezo electronics. This is due to a unique property of piezoelectric materials, wherein the piezoelectric materials deform when subjected to an electric field or generate an electric field when mechanically deformed.

As another non-limiting example, the control TLS knob can be implemented with an additional bias pad (e.g., electrodes) to supply an electric field. The bias pads can be used to apply localized electric fields or potentials to specific regions of the TLS environment, allowing for precise control over the TLS energy levels, transition frequencies, or coherence properties. In various embodiments, by adjusting voltages applied to the bias pads, the electric fields experienced by the TLSs can be modulated.

As yet another non-limiting example, the control TLS knob can be implemented by supplying off-resonant stark shift tone to the qubit of interest to shift frequency of the qubit. The off-resonant stark shift tone leverages the Stark effect (e.g., the energy levels of a quantum system are shifted in the presence of an electric field, even when the frequency of the field is detuned from the natural resonance frequency of the system) by applying an external electromagnetic field to shift the frequency of the qubit.

In any case, the control TLS knob can facilitate modulation of the qubit-TLS interaction landscape by adjusting various aspects of the qubit-TLS interaction landscape. In particular, the control TLS knob can facilitate modulation of the qubit-TLS interaction landscape wherein such modulation causes each repetition of execution of the quantum circuitto sample a different TLS environment for data collection (e.g., obtaining of measurements). Therefore, the measurements can be stabilized by accumulating and averaging it over the different TLS environments.

In various embodiments, the calibration componentcan determine a set of calibration parameters of the control TLS knob for modulating the TLS landscape for which the control TLS knob can implement during execution to omit parameters of the control TLS knob that exhibit unstable or undesirable observed measurables.

In various embodiments, the methods described herein can be extended to multi-qubit scenarios. More specifically, more than one control TLS knob can be implemented to independently control more than one respective qubit. Each of the more than one control TLS knob can individually control and modulate the qubit-TLS interaction landscape for the respective qubit. Such embodiment can enable effective and efficient characterization of a quantum device by obtaining measurements of the more than one qubit of a device in shorter durations than current methods, and thus better enable understanding of device fabrication. For example, it can be efficiently determined which qubits perform better to understand which materials, processes and geometries are desirable. Furthermore,

Systemcan unlock new capabilities in quantum computing. For example, systemcan provide for efficient execution for characterizing qubits and reducing noise. Further, systemcan allow real-time decision making in quantum computing, including qubit characterization, quantum error mitigation and quantum error correction. Systemcan additionally provide improved hardware efficiency and faster development by reducing execution time or reducing the number of devices needed to characterize the quantum system. In general, systemcan enable efficient and stabilized qubit characterization against background fluctuations and temporal fluctuations of TLSs.

Turning to, one or more embodiments described herein can include one or more devices, systems and/or apparatuses that can provide a process to facilitate modulation of the TLS landscape. Accordingly, at, illustrated is a block diagram of an example, non- limiting systemthat can at least partially facilitate such a process. While referring here to one or more processes, facilitations and/or uses of the non-limiting system, description provided herein, both above and below, also can be relevant to one or more other non-limiting systems described herein, such as the non-limiting systems.

As illustrated at, the non-limiting systemcan comprise a quantum systemthat can be employed with or separate from the classical system.

Generally, the quantum system(e.g., quantum computer system, superconducting quantum computer system and/or the like) can employ quantum algorithms and/or quantum circuitry, including computing components and/or devices, to perform quantum operations and/or functions on input data to produce results that can be output to an entity. The quantum circuitry can comprise quantum bits (qubits), such as multi-bit qubits, physical circuit level components, high level components and/or functions. The quantum circuity can comprise physical pulses that can be structured (e.g., arranged and/or designed) to perform desired quantum functions and/or computations on data (e.g., input data and/or intermediate data derived from input data) to produce one or more quantum results as an output. The quantum results, e.g., quantum measurement readout, can be responsive to the quantum job requestand associated input data and can be based at least in part on the input data, quantum functions and/or quantum computations.

In one or more embodiments, the quantum systemcan comprise components, such as a quantum operation component, a quantum processor, pulse component(e.g., a waveform generator) and/or a readout electronics(e.g., readout component). In one or more other embodiments, the readout electronicscan be comprised at least partially by the classical systemand/or be external to the quantum system. The quantum processorcan comprise one or more, such as plural, qubits. Individual qubitsA,B andC, for example, can be fixed frequency and/or single junction qubits, such as transmon qubits.

In one or more embodiments, a memoryand/or processorcan be associated with the quantum operation component, where suitable. The processorcan be any suitable processor. The processorcan generate one or more instructions for controlling the one or more processes of the quantum operation component.

The quantum operation componentcan obtain (e.g., download, receive, search for and/or the like) a quantum job requestrequesting execution of one or more quantum programs and/or a physical qubit layout. The quantum job requestcan be provided in any suitable format, such as a text format, binary format and/or another suitable format. In one or more embodiments, the quantum job requestcan be obtained by a component other than of the quantum system, such as a by a component of the classical system.

The quantum operation componentcan determine mapping of one or more quantum logic circuits for executing a quantum program. In one or more embodiments, the quantum operation componentand/or quantum processorcan direct the waveform generatorto generate one or more pulses, tones, waveforms and/or the like to affect one or more qubits, such as in response to a quantum job request.

The waveform generatorcan generally cause the quantum processorto perform one or more quantum processes, calculations and/or measurements by creating a suitable electro-magnetic signal. For example, the waveform generatorcan operate one or more qubit effectors, such as qubit oscillators, harmonic oscillators, pulse generators and/or the like to cause one or more pulses to stimulate and/or manipulate the state(s) of the one or more qubitscomprised by the quantum system.

The quantum processorand a portion or all of the waveform generatorcan be contained in a cryogenic environment, such as generated by a cryogenic environment, such as effected by a dilution refrigerator. Indeed, a signal can be generated by the waveform generatorto affect one or more of the plurality of qubits. Where the plurality of qubitsare superconducting qubits, cryogenic temperatures, such as about 4K or lower, can be employed for function of these physical qubits. Accordingly, one or more elements of the readout electronicsalso can be constructed to perform at such cryogenic temperatures.

The readout electronics, or at least a portion thereof, can be contained in the cryogenic environment, such as for reading a state, frequency and/or other characteristic of qubit, excited, decaying or otherwise.

It is noted that the aforementioned description(s) refer(s) to the operation of a single set of instructions run on a single qubit. However, scaling can be achieved. For example, instructions can be calculated, transmitted, employed and/or otherwise used relative to one or more qubits (e.g., non-neighbor qubits) in parallel with one another, one or more quantum circuits in parallel with one another, and/or one or more qubit mappings in parallel with one another.

illustrates a diagram of an example, non-limiting implementationof periodic modulation of the control TLS knob during execution of the quantum circuit in accordance with one or more embodiments described herein. One or more embodiments described with reference tocan be performed by one or more components ofand/or. Repetitive description of like elements and/or processes employed in respective embodiments is omitted for sake of brevity.